Related Covariates Research Articles

Theoretical Foundations of Multi-Product Prices Optimization Model (Part1)

The paper investigates and analyses the technologies and the methods for price optimization in a multi-product environment, where the firms face more difficulties to make an optimal decisions. Multi-Product Prices Optimization (MPPO) problem emerges specific problems, because of both prices and demands, being random variables, may exhibit different covariate relationships, determined by means of substitutional and complimentarity effects. The system of covariate relationships, determined by means of substitution and complimentarity processes, is represented as the system of multivariance regression equations. MPPO problem have been reduced to the maximization problem of the objective function of Total Revenue, which is a quadratic form. In multidimensional cases one faces the problem of absence of local maximum of Total Revenue function. The simple criterion of existing the optimal solution ofthe MPPO problem is suggested. In the case of absence of the strict maximum of Total Revenue function, parameters should be calculated on the base of OPPO model, that is on the base of independent paired problems. The represented theory can be used as a basis for development of a relevant software.Keywords: complementarity, multi-product pricing, price optimization, single-product pricing, substitution, total revenueJEL: M21

Serum 25-Hydroxyvitamin D were associated with higher risk of both albuminuria and impaired GFR incidence: a cohort study based on CLHLS study

BackgroundThis study aimed to examine the relationship between 25-hyfromxyvitamin D (25OHD) and chronic kidney disease (CKD) incidence.MethodsAll the elderly who had participated both in the 2011–2012 survey and 2014 survey in the Chinese Longitudinal Healthy Longevity Survey (CLHLS), and have biomarker data were included in the analysis. We studied those without CKD with complete data at 2011–2012 waves. Serum 25-Hydroxyvitamin D was assessed at baseline. Cox proportional risk model was used to evaluate associations between serum 25-Hydroxyvitamin D and CKD (including both albuminuria and impaired eGFR) incidence after adjusted for potential confounding..ResultsDuring the follow-up years, 255 incident cases of CKD were diagnosed. Those who developed CKD had relatively lower serum 25(OH)D (mean 37.63 vs.51.36 nmol/L, p < 0.001) compared with those who remained free of CKD. Each 1 nmol/L increase in 25(OH)D was associated with 3.4% reduced risk of CKD (HR = 0.966, 95%CI: 0.959–0.973) after adjusted for related covariates. The HRs of each 1 nmol/L increase in 25(OH)D for albuminuria and impaired eGFR were 0.952(95%CI: 0.941–0.963) and 0.975(95%CI: 0.966–0.983) respectively. When use the classifications (sufficiency, insufficiency, deficiency) or quintiles of baseline 25(OH)D levels in the Cox model, the corresponding HRs showed an increasing trend along with the decrease of baseline 25(OH)D levels (p for trend < 0.001).ConclusionsHigher 25(OH)D levels were inversely and independently associated with CKD incidence among Chinese elderly. The trend for the observed linear relationship b was most pronounced among the lowest quintile.

Dual-Domain Audio Watermarking Algorithm Based on Flexible Segmentation and Adaptive Embedding

This paper proposes a novel dual-domain audio watermarking approach based on flexible segmentation and adaptive embedding aimed to improve robustness and imperceptibility. Compared with conventional watermarking strategies, the proposed approach has two advantages. First, a novel audio beat detection approach is designed to flexibly segment the audio, which provides stronger robustness to synchronization attacks. The audio is decomposed by the discrete wavelet packet transform. Then, the covariance relationships of the decomposition coefficients at different time instants are calculated to determine the locations of the beats and to establish a flexible segmentation model. Second, a dual-domain embedding approach is proposed to realize better robustness to compression attacks while maintaining imperceptibility. In each segment, the psychoacoustic model is used to calculate the audio masking threshold, which divides the signals into the masking signal domain and masked signal domain. The signals in the masking signal domain are robust to compression attacks, and the signals in the masked signal domain have better imperceptibility. To combine these advantages, we embed the watermark into the two domains simultaneously by using the distortion-compensated dither modulation quantization approach. To reduce the impact of the watermark on the original audio, the frequency band with the lowest mask-to-noise ratio is selected as the embedding position for each domain. Moreover, the adaptive quantization steps are calculated to control the embedding strength according to the masking effect. The adaptive embedding will improve the robustness to compression attacks without significantly affecting the original audio quality. The effectiveness of our approach is verified through simulation experiments.

Implementation of an occupancy-based monitoring protocol for a widespread and cryptic species, the New England cottontail (Sylvilagus transitionalis)

Context Designing effective long-term monitoring strategies is essential for managing wildlife populations. Implementing a cost-effective, practical monitoring program is especially challenging for widespread but locally rare species. Early successional habitat preferred by the New England cottontail (NEC) has become increasingly rare and fragmented, resulting in substantial declines from their peak distribution in the mid-1900s. The introduction of a possible competitor species, the eastern cottontail (EC), may also have played a role. Uncertainty surrounding how these factors have contributed to NEC declines has complicated management and necessitated development of an appropriate monitoring framework to understand possible drivers of distribution and dynamics. Aims Because estimating species abundance is costly, we designed presence–absence surveys to estimate species distributions, test assumptions about competitive interactions, and improve understanding of demographic processes for eastern cottontails (EC) and New England cottontails (NEC). The survey protocol aimed to balance long-term management objectives with practical considerations associated with monitoring a widespread but uncommon species. Modelling data arising from these observations allow for estimation of covariate relationships between species status and environmental conditions including habitat and competition. The framework also allows inference about species status at unsurveyed locations. Methods We designed a monitoring protocol to collect data across six north-eastern USA states and, using data collected from the first year of monitoring, fit a suite of single-season occupancy models to assess how abiotic and biotic factors influence NEC occurrence, correcting for imperfect detectability. Key results Models did not provide substantial support for competitive interactions between EC and NEC. NEC occurrence patterns appear to be influenced by several remotely sensed habitat covariates (land-cover classes), a habitat-suitability index, and, to a lesser degree, plot-level habitat covariates (understorey density and canopy cover). Conclusions We recommend continuing presence–absence monitoring and the development of dynamic occupancy models to provide further evidence regarding hypotheses of competitive interactions and habitat influences on the underlying dynamics of NEC occupancy. Implications State and federal agencies responsible for conserving this and other threatened species can engage with researchers in thoughtful discussions, based on management objectives, regarding appropriate monitoring design to ensure that the allocation of monitoring efforts provides useful inference on population drivers to inform management intervention.

Like (Grand)Parent, Like Child? Multigenerational Mobility Across the EU

This study shows that the intergenerational transmission of inequality in most of the 28 EU countries is higher than what a parent-to-child paradigm would suggest. While a strand of the literature claims that this is due to a direct grandparental effect, economic historian Gregory Clark maintains that multigenerational mobility follows a Markovian process. In his view, previous estimates of social status persistence are not only (severely) attenuated by an errors-in-variables problem, but are also constant across time and space. Using a survey covering all 28 EU countries, we provide evidence against such a universal law of mobility.We show that, while in most EU countries traditional estimates of social status persistence are indeed downward biased, there are sizable differences across countries driven by country-specific factors. Further, for a few EU countries we cannot reject the hypothesis of a direct grandparental effect after accounting for a number of parents related covariates possibly affecting the multigenerational transmission process.

Occupancy of freshwater turtles across a gradient of altered landscapes

ABSTRACTTurtles are one of the most threatened groups of vertebrates worldwide. In the northeastern United States, a legacy of centuries of dramatic landscape alteration has affected freshwater turtle populations, but the relationships between the current landscape and distributions and abundances of freshwater turtles remain poorly understood. We used a stratified random approach to select 88 small, isolated wetlands across a gradient of forest cover throughout Rhode Island, USA, and systematically sampled freshwater turtles in these wetlands. We report estimates of relative abundance and used a canonical correspondence analysis to investigate relationships between species relative abundance and environmental covariates. We also investigated which environmental covariates affect the occurrence and detection probabilities of each species. Eastern painted turtles (Chrysemys picta picta) and common snapping turtles (Chelydra serpentina) were widespread (occurring in 83% and 63% of wetlands, respectively) and relatively abundant. Spotted turtles (Clemmys guttata) were far less common, occurring in 8% of wetlands, and exhibited a positive association with shallow wetlands surrounded by forest. Non‐native red‐eared sliders (Trachemys scripta elegans) occurred in 10% of wetlands and exhibited a positive association with road density, likely reflecting a positive relationship between slider occurrence and human population density. Identifying landscape‐scale habitat features that are associated with the occurrence of sensitive species can improve the ability of biologists to identify and protect turtle populations. © 2018 The Wildlife Society.

Non-parametric frailty Cox models for hierarchical time-to-event data.

SummaryWe propose a novel model for hierarchical time-to-event data, for example, healthcare data in which patients are grouped by their healthcare provider. The most common model for this kind of data is the Cox proportional hazard model, with frailties that are common to patients in the same group and given a parametric distribution. We relax the parametric frailty assumption in this class of models by using a non-parametric discrete distribution. This improves the flexibility of the model by allowing very general frailty distributions and enables the data to be clustered into groups of healthcare providers with a similar frailty. A tailored Expectation–Maximization algorithm is proposed for estimating the model parameters, methods of model selection are compared, and the code is assessed in simulation studies. This model is particularly useful for administrative data in which there are a limited number of covariates available to explain the heterogeneity associated with the risk of the event. We apply the model to a clinical administrative database recording times to hospital readmission, and related covariates, for patients previously admitted once to hospital for heart failure, and we explore latent clustering structures among healthcare providers.

On the Choice of Momentum Control Variables and Covariance Modeling for Mesoscale Data Assimilation

Abstract For mesoscale variational data assimilation with high-resolution observations, there has been an issue concerning the choice of momentum control variables and related covariance modeling. This paper addresses the theoretical aspect of this issue. First, relationships between background error covariance functions for differently chosen momentum control variables are derived, and different choices of momentum control variables are proven to be theoretically equivalent in the sense that they lead to the same optimally analyzed incremental wind field in the limit of infinitely high spatial resolution provided their error covariance functions satisfy the derived relationships. It is then shown that when the velocity potential χ and streamfunction ψ are used as momentum control variables with their background error autocovariance functions modeled by single-Gaussian functions, the derived velocity autocovariance functions contain significant negative sidelobes. These negative sidelobes can represent background wind error structures associated with baroclinic waves on the synoptic scale but become unrepresentative on the mesoscale. To reduce or remove these negative sidelobes for mesoscale variational data assimilation, Gaussian functions are used with two types of modifications to model the velocity covariance functions in consistency with the assumed homogeneity and isotropy in variational data assimilation. In this case, the random (χ, ψ) background error fields have no classically valid homogeneous and isotropic covariance functions, but generalized (χ, ψ) covariance functions can be derived from the modified velocity covariance functions for choosing (χ, ψ) as momentum control variables. Mathematical properties of generalized covariance functions are explored with physical interpretations. Their important implications are discussed for mesoscale data assimilation.

808: Oxytocin regimen for induction of labor and pregnancy outcomes

Uncertainty exists regarding the optimal oxytocin dose regimen for induction of labor (IOL). We evaluated the association of oxytocin regimen for IOL with cesarean delivery and with adverse perinatal composite outcome in low-risk nulliparous women. Secondary analysis of a multi-center randomized control trial of IOL at 39 weeks compared with expectant management in low-risk nulliparous women. Women in either group who underwent IOL with a mid-to high-dose oxytocin (MHD) regimen were compared with those induced with a low-dose oxytocin (LD) regimen. The primary outcomes were cesarean delivery and a composite of perinatal death or severe neonatal complications (Table 1). M ultivariable regression was used to estimate relative risks (RR) controlling for related covariates, although site could not be adjusted for given collinearity with oxytocin regimen. Interaction between oxytocin regimen and modified Bishop score, induction indication and treatment group were also evaluated. Of 6,106 women enrolled in the primary trial, 3,034 women underwent induction with oxytocin; 889 in the MHD group and 2145 in the LD group. There was a shorter duration from start of oxytocin to delivery (median 11.7 hours vs. 13.4 hours) and higher percentage of women in the lowest quartile for time to delivery in the MHD group compared with the LD group (p<0.001 for both). The lower frequency of cesarean delivery in the MHD group (20.9% vs. 25.0%) was not significant after adjustment (Table 1). There was an increase in operative vaginal delivery in the MHD group (9.7% vs. 6.8%, P=0.007). The adverse perinatal composite outcome was significantly more frequent in the MHD group (6.6% vs. 4.3%, adjusted RR 1.59, 95% CI (1.15-2.21)) compared with LD group; this association was most notable among those with an elective induction (p=0.03 for interaction). The higher frequency of the adverse perinatal outcome in the MHD group was mostly due to a higher frequency of continuous positive airway pressure or high-flow nasal cannula (Table 2). Compared with LD regimen, MHD regimen for induction was associated with a similar chance of spontaneous vaginal delivery as well as a higher risk of an adverse perinatal composite outcome, particularly for elective induction. It remains uncertain if this finding is related to the actual regimen or other confounding variables such as site of use.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Impact of Regional Cardiocerebrovascular Centers on Myocardial Infarction Patients in Korea: A Fixed-effects Model.

ObjectivesThe Regional Cardiocerebrovascular Center (RCCVC) Project designated local teaching hospitals as RCCVCs, in order to improve patient outcomes of acute cardiocerebrovascular emergencies by founding a regional system that can adequately transfer and manage patients within 3 hours. We investigated the effects of RCCVC establishment on treatment volume and 30-day mortality.MethodsWe constructed a panel dataset by extracting all acute myocardial infarction cases that occurred from 2007 to 2016 from the Health Insurance Review and Assessment Service claims data, a national and representative source. We then used a panel fixed-effect model to estimate the impacts of RCCVC establishment on patient outcomes.ResultsWe found that the number of cases of acute myocardial infarction that were treated increased chronologically, but when the time effect and other related covariates were controlled for, RCCVCs only significantly increased the number of treatment cases of female in large catchment areas. There was no statistically significant impact on 30-day mortality.ConclusionsThe establishment of RCCVCs increased the number of treatment cases of female, without increasing the mortality rate. Therefore, the RCCVCs might have prevented potential untreated deaths by increasing the preparedness and capacity of hospitals to treat acute myocardial infarction patients.

1340. Population Pharmacokinetic (PK) Analysis of APX001 Using Phase 1 Data

BackgroundAPX001 is a novel antifungal agent which is rapidly converted to the active metabolite APX001A. APX001A exhibits in vitro activity against many clinically important yeast and fungi, including echinocandin- and azole-resistant Candida species. Given this activity, intravenous (IV) and oral (PO) formulations of APX001 are being developed for the treatment of patients with candidemia or invasive candidiasis. Phase 1 data were used to develop a population PK (PPK) model to describe the time-course of APX001A in plasma.MethodsThe PPK model was developed using 3,736 plasma PK samples collected from 128 healthy subjects who received APX001 single and multiple IV and PO doses ranging from 10 to 1,000 mg. Instantaneous conversion was assumed by scaling input doses by the molecular weight ratio of APX001A to APX001. After development of the structural PK model, stepwise forward and backward selection procedures were used to identify significant covariate relationships. Model qualification included standard goodness-of-fit metrics and prediction-corrected visual predictive check (PC-VPC) plots.ResultsA two-compartment model with zero-order IV input, or first-order PO absorption with lag time to account for the apparent delay in oral absorption, best described APX001A plasma PK. Exponential error models were used to estimate interindividual variability (IIV) for all parameters. Interoccasion variability was estimated for the absorption rate constant, bioavailability, and lag time. Body weight was identified as a statistically significant predictor of the IIV on the volume of the central and peripheral compartments. The PPK model provided an accurate and unbiased fit to the plasma data based on individual- and population-predicted concentrations (r2 = 0.977 and 0.873, respectively). The PC-VPC plots for the final PPK model (Figure 1) demonstrated good alignment between observed concentrations and the model predicted 5th, 50th, and 95th percentiles.ConclusionA PPK model describing APX001A plasma PK following IV or PO doses was successfully developed. This model will be useful for generating simulated APX001A exposures for use in pharmacokinetic–pharmacodynamic target attainment analyses to support APX001 dose selection. Disclosures M. Trang, Amplyx Pharmaceuticals, Inc.: Research Contractor, Research support. J. C. Bader, Amplyx Pharmaceuticals, Inc.: Research Contractor, Research support. E. A. Ople, Amplyx Pharmaceuticals, Inc.: Employee, Salary. W. G. Kramer, Amplyx Pharmaceuticals, Inc.: Scientific Advisor, Consulting fee. M. R. Hodges, Amplyx Pharmaceuticals, Inc.: Employee, Salary. S. M. Bhavnani, Amplyx Pharmaceuticals, Inc.: Research Contractor, Research support. C. M. Rubino, Amplyx Pharmaceuticals, Inc.: Research Contractor, Research support.

Relaciones funcionales y estrategias de alumnos de primero de Educación Primaria en un contexto funcional

Desde un enfoque funcional del álgebra escolar, en este trabajo indagamos sobre el pensamiento funcional de alumnos de primero de Educación Primaria (6 años) en el contexto español. Particularmente, nos centramos en las relaciones funcionales y las estrategias que emplean estos alumnos en la resolución de problemas que involucran funciones. Analizamos parte de la información recogida en un experimento de enseñanza con un grupo de treinta alumnos y entrevistas individuales a cuatro de estos alumnos. Encontramos que la relación funcional más frecuentemente identificada es la correspondencia. Algunos alumnos también identifican la relación de covariación. Además, se evidencia un vínculo entre ambas relaciones funcionales y las estrategias de operatoria y/o conteo.

The U-Shaped Association between Bilirubin and Diabetic Retinopathy Risk: A Five-Year Cohort Based on 5323 Male Diabetic Patients.

Aims This study aimed at assessing the impact of baseline bilirubin (TBiL) on the incidence of diabetic retinopathy (DR) based on a five-year cohort study which consisted of 5323 Chinese male diabetic patients. Methods A cohort study based on 5323 male diabetic patients was conducted in Beijing, from 2009 to 2013. Both baseline TBiL and follow-up changes were measured. Cox proportional risk model was used to calculate the hazard ratio (HR) of TBiL for DR risk. Results During the follow-up period, there were 269 new DR cases. The incidence of five-year follow-up was 5.1% (95% CI: 4.5%~5.6%). The TBiL level of those who had diabetic retinopathy was lower than that of those without (12.51+ 1.20 mol/L and 13.11+ 1.32 μmol/L, P = 0.033). And more interestingly, along with the quintiles of baseline TBiL, there showed a U-shaped curve with DR incidence. And the RRs were 0.928 (95% CI: 0.646–1.331), 0.544 (95% CI: 0.365–0.811), 0.913 (95% CI: 0.629–1.324), and 1.035 (95% CI: 0.725–1.479) for the second, third, fourth, and fifth quintiles of baseline TBiL levels, respectively, compared with the first quintile. For follow-up TBiL changes, after being adjusted for related covariables and baseline TBiL levels (as continuous variable) in the model, the RRs for DR were 1.411 (95% CI: 1.081–1.842) for those who had decreased TBiL level and 0.858 (95% CI: 0.770–0.947) for those who had increased TBiL level during follow-up. And this association was more prominent among those with lower baseline TBiL level. Conclusions Serum TBiL had a U-shaped relationship with DR incidence, which was independent of control status of diabetes and other related covariates.

Population Pharmacokinetics of Tacrolimus in Transplant Recipients: What Did We Learn About Sources of Interindividual Variabilities?

Tacrolimus, a calcineurin inhibitor, is a common immunosuppressant prescribed after organ transplantation and has notable inter- and intrapatient pharmacokinetic variability. The sources of variability have been investigated using population pharmacokinetic modeling over the last 2 decades. This article provides an updated synopsis on published nonlinear mixed-effects analyses developed for tacrolimus in transplant recipients. The objectives were to establish a detailed overview of the current data and to investigate covariate relationships determined by the models. Sixty-three published analyses were reviewed, and data regarding the study design, modeling approach, and resulting findings were extracted and summarized. Most of the studies investigated tacrolimus pharmacokinetics in adult and pediatric renal and liver transplants after administration of the immediate-release formulation. Model structures largely depended on the study sampling strategy, with ∼50% of studies developing a 1-compartment model using trough concentrations and a 2-compartment model with delayed absorption from intensive sampling. The CYP3A5 genotype, as a covariate, consistently impacted tacrolimus clearance, and dosing adjustments were required to achieve similar drug exposure among patients. Numerous covariates were identified as sources of interindividual variability on tacrolimus pharmacokinetics with limited consistency across these studies, which may be the result of the study designs. Additional analyses are required to further evaluate the potential impact of these covariates and the clinical implementation of these models to guide tacrolimus dosing recommendations. This article may be useful for guiding the design of future population pharmacokinetic studies and provides recommendations for the selection of an existing optimal model to individualize tacrolimus therapy.

Application of a Principal Component Analysis, (PCA), Based on the Macroeconomic Factors, Namely, Personal Consumption Expenditures, Gross Private Domestic Investment, Net Export of Goods and Services and Government Consumption Expenditures and Gross Investment that Constitute The US GDP.

In this article, we have tested the correlation and covariance relationships that the natural logarithmic yearly returns of the macroeconomic variables in terms of personal consumption expenditures, gross private domestic investment, net export of goods and services and government consumption expenditures and gross investment, have on the US Gross domestic product, (GDP). We have applied a principal component analysis, (PCA), in EViews 6 to check the eigenvalues, the eigenvectors loadings of the correlation matrix and the covariance matrix. The aim by using this methodology is twofold. Firstly, to identify the degree of correlation between the variables. Secondly to reduce the dimension of variation between the variables by eliminating the factors. We have found though the correlation matrix that most of the correlation coefficients of the macroeconomic variables are greater than 0.5 and they show very strong positive linear correlation. There is also linear weak negative and positive correlation between the macro variables. In terms of dimensionality reduction, we have found that factors 1 and 2 have an eigenvalues greater than 1. Specifically, factor 1 has a value of 3.14 and factor 2 has a value of 1.09. Thus, the factors that we will retain are two. Concerning, eigenvalues figures, we have found that the proportion for factor 1 is 62.73% and for factor 2 is 21.74% of the total variance. The first two components namely account for 84.47% of the total variation. Most of the residuals of the common covariance matrix are positive, which mean that the variables increase together. The orthonormal loadings biplot shows that the first component has the highest proportion of total variation, which is 62.7% and positive loadings for all five variables. The second component has a value of 21.7% of total variation. It has a positive variable loadings for government consumption expenditures and gross investment, (GCEGI) and negative variable loadings for gross private domestic investment, (GPDI), and net export of goods and services, (NEGS). The total dataset includes annual data starting from 1980 to 2012 and total to 33 observations. The total data of the logarithmic yearly returns account to 32 observations. The data was obtained from the US Bureau of Economic Analysis, (BEA).

The perspectives of politicians on tobacco control in Turkey.

BackgroundTobacco use is a leading but preventable cause of non-communicable diseases and premature death. The legislature has a key role in setting tobacco control policies. Smoking trends are decreasing thanks to the introduction of effective tobacco control policies in Turkey and these policies may have been shaped by how politicians’ interpreted social problems that were prominent during the development and implementation of tobacco regulations.AimThis paper explores the long-term national relationship between tobacco consumption, tobacco control policies and the associated political discourse in Turkey, considering the varying influences through national leadership on this important public health agenda. This relationship is studied by comparing a time series analysis of tobacco consumption trends with a policy analysis of the minutes of deliberations at the Grand National Assembly of Turkey (GNAT).MethodsThis study uses Bayesian time series analysis in order investigate whether the tobacco control policies and related activities influenced the annual per adult cigarette consumption in Turkey. We used a novel method to identify change points in tobacco trends and whether they correspond with key policy changes intended to alter usage after adjusting for the effect of other non-policy related covariates, such as the purchasing power. The policy analysis included an examination of the minutes of deliberations at the GNAT—which is the Turkish parliament and unicameral Turkish legislature—1 year before and 1 year after the break years associated with an increase or decrease in tobacco consumption.Results and recommendationsTobacco consumption increased with the encouragement of tobacco production and the entrance of multinational companies in the country in 1976 and 1993, respectively. The National Tobacco Law of 1996 and comprehensive amendments in 2008, including smoke-free public places and tax increases, appear to have helped reduce tobacco consumption in Turkey. The focus of Parliamentary discussions throughout this period changed, becoming less supportive of tobacco over time. However, throughout the period there remained discussions focussing on concerns around the implications for the economy and the privatization agenda, national agriculture and the welfare of farmers. Effective control appears to require certain political ingredients to be implemented: politicians who are well informed on tobacco control measures and understand the range of issues surrounding the policies (not only those directly health-related); and supportive public health information in the community. Evidence-based public health policy should be introduced to the politicians.

Associations Between Race, Perceived Psychological Stress, and the Gut Microbiota in a Sample of Generally Healthy Black and White Women: A Pilot Study on the Role of Race and Perceived Psychological Stress.

Racial health disparities persist among black and white women for colorectal cancer. Understanding racial differences in the gut microbiota and related covariates (e.g., stress) may yield new insight into unexplained colorectal cancer disparities. Healthy non-Hispanic black or white women (age ≥19 years) provided survey data, anthropometrics, and stool samples. Fecal DNA was collected and isolated from a wipe. Polymerase chain reaction was used to amplify the V4 region of the 16SrRNA gene and 250 bases were sequenced using the MiSeq platform. Microbiome data were analyzed using QIIME. Operational taxonomic unit data were log transformed and normalized. Analyses were conducted using linear models in R Package "limma." Fecal samples were analyzed for 80 women (M (SD) age = 39.9 (14.0) years, 47 black, 33 white). Blacks had greater average body mass index (33.3 versus 27.5 kg/m, p < .01) and waist circumference (98.3 versus 86.6 cm, p = .003) than whites. Whites reported more stressful life events (p = .026) and greater distress (p = .052) than blacks. Final models accounted for these differences. There were no significant differences in dietary variables. Unadjusted comparisons revealed no racial differences in alpha diversity. Racial differences were observed in beta diversity and abundance of top 10 operational taxonomic units. Blacks had higher abundances than whites of Faecalibacterium (p = .034) and Bacteroides (p = .038). Stress was associated with abundances of Bifidobacterium. The association between race and Bacteroides (logFC = 1.72, 0 = 0.020) persisted in fully adjusted models. Racial differences in the gut microbiota were observed including higher Bacteroides among blacks. Efforts to cultivate an "ideal" gut microbiota may help reduce colorectal cancer risk.

Estimating soil salinity from remote sensing and terrain data in southern Xinjiang Province, China

Soil salinization is one of the main reasons for soil health and ecosystem deterioration in most degraded arid and semiarid areas. To monitor its spatial variation as precise as possible over a large area, we collected 225 samples using traditional field experiment and laboratory analysis method from the southern part of the Xinjiang Province, China, affected by soil salinity under strong arid climate. Then, we constructed both Cubist and partial least square regression (PLSR) models on electrical conductivity (EC) (150 ground-based measurements as calibration set) using various related covariates (e.g. terrain attributes, remotely sensed spectral indices of vegetation and salinity from landsat8 OLI satellite) that are at the same time period corresponding to soil sampling. Two models were validated using remaining 75 independent ground based measurements and were then used to map the soil salinity over the study area. Finally, the validation results of two models were compared under different intervals of EC, soil moisture content and vegetation coverage. The results indicated that Cubist model could predict EC value with better accuracy and stability under variable environment than PLSR. The R2, RMSE, MAE and RPD of the Cubist model were 0.91, 5.18 dS m−1, 3.76 dS m−1 and 3.15 while corresponding values of the PLSR model were 0.66, 10.46 dS m−1, 8.21 dS m−1 and 1.56 in validation dataset, respectively. Additionally, the map derived from Cubist model revealed more detailed variation information of the spatial distribution of EC than that from PLSR model across the study area. Thus, Cubist model was recommended for mapping soil salinity using indices derived from satellite and terrain in other arid areas.

Bilirubin and its changes were negatively associated with diabetic kidney disease incidence and progression: A five-year's cohort study based on 5323 Chinese male diabetic patients

AimsThis study aimed to evaluate the association between baseline bilirubin (TBiL) and follow-up TBiL changes for diabetic kidney disease (DKD) incidence and progression based on a 5 years' cohort study. MethodsThis cohort study was conducted in Beijing between 2009 and 2013. The subjects were consisted of 5342male diabetic patients with baseline retinopathy. Cox proportional risk model was used to calculate hazards ratio (HR). ResultsThe mean age of the 5342 diabetic patients was 78.68 ± 8.40 (65–102 yrs). The total five year incidence was 8.7% (95%CI: 7.9%–9.4%) for DKD and 10.5% (95%CI: 9.7%–11.3%) for eGFR decrease. The HR of baseline TBiL showed a decreasing trend for both DKD incidence and eGFR decrease. The HRs of baseline TBiL (per μmol/L increase) for DKD and eGFR decrease were 0.967(95%CI: 0.946–0.988) and 0.955(95%CI: 0.936–0.975) respectively. For follow-up TBiL changes, after adjusted for related co-variables and baseline TBiL levels (as continuous variable) in the model, the HRs (per μmol/L of follow-up TBiL changes) for DKD and eGFR decrease were 0.973(95%CI: 0.952–0.995) and 0.991(95%CI: 0.974–0.998) respectively. The results were similar when baseline TBiL and follow-up TBiL changes were used as tertiary variable. ConclusionNot only baseline TBiL, but also follow-up changes were significantly associated with DKD incidence and progression.

Risk-adjusted monitoring of surgical performance.

We propose a nonparametric risk-adjusted cumulative sum chart to monitor surgical outcomes for patients with different risks of post-operative mortality due to risk factors that exist before the surgery. Using varying-coefficient logistic regression models, we accomplish the risk adjustment. Unknown coefficient functions are estimated by global polynomial spline approximation based on the maximum likelihood principle. We suggest a bisection minimization approach and a bootstrap method to determine the chart testing limit value. Compared with the previous (parametric) risk-adjusted cumulative sum chart, a major advantage of our method is that the morality rate can be modeled more flexibly by related covariates, which significantly enhances the monitoring efficiency. Simulations demonstrate nice performance of our proposed procedure. An application to a UK cardiac surgery dataset illustrates the use of our methodology.